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Abstract  

The preparation of rutile type solid solutions in (TiO2)x -(RuO2)1−x system in the 0≤x ≤0.7 concentration range is described. The single phase solid solutions are formed by controlled nanocrystallization of amorphous gels prepared by the sol-gel method. The kinetics of this crystallization process has been analyzed. It was found that the crystallization does not correspond to the Johnson-Mehl-Avrami model and it can be described by the two-parameter Šestk-Berggren kinetic model.

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Solid solutions in the MgO-Al2O3-Cr2O3 system

Effects of polymorphism, temperature and pressure

Journal of Thermal Analysis and Calorimetry
Authors: A. Turkin and V. Drebushchak

Abstract  

Coexisting solid solutions with spinel and corundum structure were synthesized at 1773 K and two pressures, 1 bar and 25 kbar. Samples were analyzed by electron microprobe analysis and X-ray powder diffraction. Pressure and temperature were shown to affect the properties of the solid solutions in different ways. Pressure governs the composition of the defect spinel Mg1−xAl2O4, and temperature changes the cation distribution between coexisting phases. This allows one to separate the effects of cation exchange and magnetic contribution to the heat capacity in thermodynamic modeling. The defect spinel itself can form only because γ-Al2O3 exists, polymorph with spinel structure. Thermodynamic considerations argue in favor of eskolaite-spinel assemblages prevailing over corundum-picrochromite ones at very high temperatures deep in the Earth.

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Abstract  

Heat capacity of unstable quenched solid solutions (Fe1−xNix)0.96S was measured by DSC (enthalpy method and scanning heating). According to optic microscopy and X-ray powder diffraction, the samples are homogeneous phase of NiAs type with unit cell parameters changing regularly with composition. Heat capacity changes with composition irregularly due to the difference in magnetic properties of the end members: C p/1.96R=4.1 for Fe-rich samples and 3.3 for Ni-rich ones. There is no exact limit between two types of magnetic ordering. Instead, samples with intermediate composition (0.7<x<0.8) show large fluctuations in C p due to the inconsistency of alternative (FeS and NiS) types of magnetic ordering.

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Abstract  

Al2O3-Cr2O3 solid solutions with 0, 4, 7, 10 and 20 mol% of corundum were synthesized using a high-pressure/high-temperature apparatus and characterized by X-ray powder diffraction. Calorimetric measurements were carried out using DSC-111 (Setaram). Heat capacity was measured by the enthalpy method in a temperature range of 260–340 K, near magnetic phase transition in pure Cr2O3 (305 K). Magnetic contribution into the heat capacity was derived and found to change irregularly with the composition. Heat capacity of solid solutions remains constant in a relatively wide range of composition, while the C p values of the end members differ significantly. This phenomenon is very important for the modeling of the thermodynamic functions of intermediate solid solutions.

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Abstract  

The thermal dehydration-decomposition of Ln2(SeO4)3·nH2O (wheren=12 forLn=Pr, Nd andn=8 forLn=Sm) and PrxLn2−x(SeO4)3·nH2O (wheren=12 forx=1.0 andLn=Nd;n=8 forx=0.2 and 1.0 in case ofLn=Sm) have been reported.

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Introduction Physicochemical properties of solid solutions are possible to modify, which is very important for designing of new functional materials. The knowledge on the influence of the change of composition of the solid

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Summary  

The heats of ordering for mechanochemically synthesized nano-sized supersaturated solid solutions were demonstrated for Ni-In, Ni-Sn, Ni-Al, Cu-Sn, Cu-Hg systems. It is shown that increasing concentration of doping element leads to decreasing of decomposition temperature and to increasing of decomposition enthalpy. The concentration heterogeneity of doping elements in mechanochemically synthesized supersaturated solid solutions was found. The reactivity of alloys Cu 20 mass % Sn for commercial powder and MA powder was investigated.

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Journal of Thermal Analysis and Calorimetry
Authors: A. Ianculescu, A. Braileanu, M. Zaharescu, I. Pasuk, E. Chirtop, C. Popescu, and E. Segal

Abstract  

It is well known that the manganites-based solid solutions are interesting for their electric and magnetic properties. LaMnO3 exhibits a distorted perovskite structure due to Mn3+ ion, which determines the presence of the Jahn–Teller effect. Replacing La3+ host ions by cations of lower valence leads to the disappearance of this effect and changes the characteristics of these materials. Although the formation of manganites-based solid solutions has been intensively studied, there are some unelucidated aspects concerning their formation mechanism, depending both on the precursors used and on the thermal treatment applied in order to obtain suitable properties. In this work the formation mechanism of La0.7M0.3MnO3 (M=Ca, Sr, Ca+Sr in equimolecular mixture) solid solutions, in isothermal and non-isothermal conditions, was studied. For this purpose XRD, DTA/TG and spectral techniques were used. The solid solutions formation was found to be more dependent on the Mn-precursors type than the thermal treatment conditions.

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Abstract  

X-ray phase analysis (XRD), differential thermal analysis (DTA) and IR spectroscopy have shown that continuous substitution solid solutionsin are formed in the FeVMoO7–CrVMoO7 system. With increasing the degree of Cr3+ ion incorporation into the FeVMoO7 structure, a crystal lattice contraction of the Fe1–xCrxVMoO7 solid solution arise. Elevation of temperature of its incongruent melting and gradual shifting of the corresponding IR absorption bands towards higher wavenumbers have been noticed, as well. The solid product of incongruent melting for x≤0.5 is the Fe4–yCryV2 Mo3 O20 solid solutions phase, whereas for x>0.5 Fe2–zCrz(MoO4)3 and Fe2–u Cru O3 solid solutions.

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Abstract  

Positron Lifetime Spectroscopy (LS) measurements were performed in a series of binary molecular solid solutions of the general formula M1–xGxL3, where L(ligand)=acetylacetone, dipivaloylmethane, or N-benzoyl-N-phenylhydroxylamine, M=Al(III), Ga(III) or In(III), as matrix, and G=Cr(III), Mn(III), Fe(III), Co(III), Ru(III), Rh(III) and Ir(III), as guest molecules, and the corresponding mechanical mixtures. For the solid solutions, the o-Ps yield values (I 3) decrease very rapidly with the increase of the guest mole fraction, showing a high efficient Ps inhibition process, while for the corresponding mechanical mixtures, these values decrease linearly with the increase of the guest molecule concentration, indicating the presence of two distinct phases. These results confirm our previous proposal that the LS technique is able to characterize solid solutions formed by one matrix, in whichI 3 values are high, and one guest, in which theI 3 values are very low.

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